There are several ways of assembling liquid crystal flat panel displays (LCD). For example, the prior art has used a method where the two substrate portions comprising the panel are first fully configured with all required thin film transistors (TFT's), circuit lines and color filters. The two substrate portions (hereinafter sometimes called "substrates") of the display panel are then aligned with respect to one another at a gap spacing on the order of about 5 microns (e.g. by using 5 micron glass spheres) and are then joined over most of peripheries using a two part pre-mixed high temperature epoxy that requires a temperature of approximately 180.degree. C., applied for several hours to cure or cross-link. After this, the resultant empty panel assembly is placed in a vacuum chamber for removal of air and then placed in a dish of liquid crystal material which is forced into the evacuated panel space by backfilling the chamber with nitrogen gas. This prior art method is described in U.S. Pat. No. 5,029,623, issued on Jul. 9, 1991 to Stefan Brosig.
Any method of assembly that uses a thermal setting epoxy can be problematic because the curing temperature is too high for the liquid crystal material to tolerate without damaging its functional characteristics. For this reason, the assembly of an empty LCD panel from two substrates must precede the step of filling the empty panel with liquid crystal material. However, since the assembled empty LCD panel has a very narrow gap (e.g. 5 to 10 microns) between the two assembled substrates that form the panel, the filling step in vacuum is extremely slow, taking on the order of 3-5 hours.
More recently, a faster fill technique ("one-drop fill") has been developed wherein one panel substrate receives a filling of droplets of liquid crystal prior to joining it with the second panel substrate. A version of the one-drop fill method is disclosed in U.S. Pat. No. 5,263,888, issued to Teruhisa Ishihara et al on Nov. 23, 1993. Here, the sealant is typically a uv (ultraviolet) setting epoxy where cross-linking requires uv radiation. This one-drop fill method cannot use the thermally setting epoxy but must use instead the uv or other epoxy which cures (sets or cross-links) near room temperature. As will be understood, this uncured epoxy must necessarily come in contact with the liquid crystal because the epoxy forms the peripheral boundary wall for the liquid crystal material. There is mounting evidence that uncured epoxy and other sealants will react with the liquid crystal causing the latter to degrade in its performance as a liquid crystal material. This deleterious effect is especially likely in those regions of the display panel where there is incomplete curing of the uv epoxy because the uv light is unable to reach all portions of the epoxy due to shadows cast by the thin film circuitry that extends out to the periphery of the panel substrates.